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Date: Wed, 23 Mar 2022 12:16:41 +0100 From: Artem Savkov <asavkov@...hat.com> To: tglx@...utronix.de, jpoimboe@...hat.com, netdev@...r.kernel.org Cc: davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org, linux-kernel@...r.kernel.org, Artem Savkov <asavkov@...hat.com> Subject: [PATCH 1/2] timer: introduce upper bound timers Add TIMER_UPPER_BOUND flag which allows creation of timers that would expire at most at specified time or earlier. This was previously discussed here: https://lore.kernel.org/all/20210302001054.4qgrvnkltvkgikzr@treble/T/#u Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com> Signed-off-by: Artem Savkov <asavkov@...hat.com> --- include/linux/timer.h | 3 ++- kernel/time/timer.c | 36 ++++++++++++++++++++++-------------- 2 files changed, 24 insertions(+), 15 deletions(-) diff --git a/include/linux/timer.h b/include/linux/timer.h index fda13c9d1256..9b0963f49528 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -67,7 +67,8 @@ struct timer_list { #define TIMER_DEFERRABLE 0x00080000 #define TIMER_PINNED 0x00100000 #define TIMER_IRQSAFE 0x00200000 -#define TIMER_INIT_FLAGS (TIMER_DEFERRABLE | TIMER_PINNED | TIMER_IRQSAFE) +#define TIMER_UPPER_BOUND 0x00400000 +#define TIMER_INIT_FLAGS (TIMER_DEFERRABLE | TIMER_PINNED | TIMER_IRQSAFE | TIMER_UPPER_BOUND) #define TIMER_ARRAYSHIFT 22 #define TIMER_ARRAYMASK 0xFFC00000 diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 85f1021ad459..60253ad9ed86 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -491,7 +491,7 @@ static inline void timer_set_idx(struct timer_list *timer, unsigned int idx) * time. */ static inline unsigned calc_index(unsigned long expires, unsigned lvl, - unsigned long *bucket_expiry) + unsigned long *bucket_expiry, bool upper_bound) { /* @@ -501,34 +501,39 @@ static inline unsigned calc_index(unsigned long expires, unsigned lvl, * - Truncation of the expiry time in the outer wheel levels * * Round up with level granularity to prevent this. + * Do not perform round up in case of upper bound timer. */ - expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl); + if (upper_bound) + expires = expires >> LVL_SHIFT(lvl); + else + expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl); + *bucket_expiry = expires << LVL_SHIFT(lvl); return LVL_OFFS(lvl) + (expires & LVL_MASK); } static int calc_wheel_index(unsigned long expires, unsigned long clk, - unsigned long *bucket_expiry) + unsigned long *bucket_expiry, bool upper_bound) { unsigned long delta = expires - clk; unsigned int idx; if (delta < LVL_START(1)) { - idx = calc_index(expires, 0, bucket_expiry); + idx = calc_index(expires, 0, bucket_expiry, upper_bound); } else if (delta < LVL_START(2)) { - idx = calc_index(expires, 1, bucket_expiry); + idx = calc_index(expires, 1, bucket_expiry, upper_bound); } else if (delta < LVL_START(3)) { - idx = calc_index(expires, 2, bucket_expiry); + idx = calc_index(expires, 2, bucket_expiry, upper_bound); } else if (delta < LVL_START(4)) { - idx = calc_index(expires, 3, bucket_expiry); + idx = calc_index(expires, 3, bucket_expiry, upper_bound); } else if (delta < LVL_START(5)) { - idx = calc_index(expires, 4, bucket_expiry); + idx = calc_index(expires, 4, bucket_expiry, upper_bound); } else if (delta < LVL_START(6)) { - idx = calc_index(expires, 5, bucket_expiry); + idx = calc_index(expires, 5, bucket_expiry, upper_bound); } else if (delta < LVL_START(7)) { - idx = calc_index(expires, 6, bucket_expiry); + idx = calc_index(expires, 6, bucket_expiry, upper_bound); } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) { - idx = calc_index(expires, 7, bucket_expiry); + idx = calc_index(expires, 7, bucket_expiry, upper_bound); } else if ((long) delta < 0) { idx = clk & LVL_MASK; *bucket_expiry = clk; @@ -540,7 +545,8 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk, if (delta >= WHEEL_TIMEOUT_CUTOFF) expires = clk + WHEEL_TIMEOUT_MAX; - idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry); + idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry, + upper_bound); } return idx; } @@ -607,7 +613,8 @@ static void internal_add_timer(struct timer_base *base, struct timer_list *timer unsigned long bucket_expiry; unsigned int idx; - idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry); + idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry, + timer->flags & TIMER_UPPER_BOUND); enqueue_timer(base, timer, idx, bucket_expiry); } @@ -1000,7 +1007,8 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option } clk = base->clk; - idx = calc_wheel_index(expires, clk, &bucket_expiry); + idx = calc_wheel_index(expires, clk, &bucket_expiry, + timer->flags & TIMER_UPPER_BOUND); /* * Retrieve and compare the array index of the pending -- 2.34.1
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